شناسایی واحدهای همگن وا کنش به اقلیم در کلانشهر تهران (مقاله علمی وزارت علوم)
درجه علمی: نشریه علمی (وزارت علوم)
آرشیو
چکیده
فضاهای شهری با ویژگی های متفاوت از محیط های طبیعی، نیازمند تجدید نظر در پهنه بندی های اقلیمی سنتی هستند تا شرایط اقلیمی در برنامه ریزی ها و مدیریت شهر، قابل استفاده باشد. شهر تهران با ویژگی های طبیعی و الگوی توسعه شهری متفاوت، پاسخ های متفاوتی در برابر شرایط اقلیمی دارد. واحد های همگن واکنش به اقلیم (HCR) طبقه بندی اقلیم شهری را بر اساس نقشه های تراکم ساختمانی و ژئومورفولوژی طبیعی زمین انجام می دهد. هدف آن تهیه نقشه ای با مجموعه ای از مناطق همگن با فضای شهری است و مزیت آن در ارائه دستورالعمل های اقلیمی برای برنامه ریزی در طرح های جامع شهری است. برای مطالعه از لایه های اطلاعات مکانی کاربری/پوشش اراضی، تراکم ساختمانی، شبکه هیدروگرافی، عناصر جوی، تراکم جمعیتی و توپوگرافی شهری استفاده گردید. نتیجه آن تهیه نقشه اقلیم شهری تهران در 17 واحد اقلیمی و به دنبال آن ارائه هشت دستورالعمل اقلیمی برای برنامه ریزی شهری است. ترکیب مورفولوژی زمین، سطوح ارتفاعی، شیب سطحی، بستر رودخانه ها با مشخصات فیزیکی و کالبدی شهری مهمترین مشخصه مدل HCR استفاده شده در پژوهش است. نتایج به دست آمده گویای واحد اقلیمی همگنی در نوار شمالی تهران در مجاورت کوهستان با مخروط افکنه ها، روددره ها، پوشش گیاهی غنی تر و رخنمون های سنگی است. در حالی که تکه تکه شدن زیستگاه ها، بافت ساختمانی فشرده، دشت رسوبی هموار مشخصه اصلی مناطق مرکزی شهر هستند. نوار میانی تهران با توالی تپه ها و دره ها از پارک جنگلی چیتگر در غرب تا تپه های گیشا، پردیسان، عباس آباد و لویزان واحد اقلیمی همگن میانی را تشکیل داده که فضاهای تنفسی شهر هستند. گسترش فیزیکی شهر در سمت ارتفاعات و به ویژه در مسیر روددره ها اغلب ظرفیت پویایی، تهویه طبیعی و گردش هوا را کاهش داده و از عوامل افزایش بار گرمای محیطی و شکل گیری جزیره گرمای شهری و تشدید آلودگی هوا در مناطق مرکزی شهر هستند.Identification of Homogeneous Climate Response Units in Tehran Metropolitan
Highlights
- Tehran exhibits significant climatic diversity due to variations in elevation, morphology, and physical features.
- The geomorphological characteristics of Tehran's substratum play a critical role in shaping homogeneous climate response units.
- The city's compact urban texture and developmental patterns contribute significantly to the formation of Tehran's urban heat island.
- The climate response units of Tehran are influenced by elevation, surface morphology, and urbanization patterns.
- The middle strip of Tehran, featuring hills and constructed parks, creates distinct local climatic conditions.
Introduction
Understanding the natural characteristics of urban areas, especially their climatic features, is crucial for effective land management. Urban climate plays a fundamental role in shaping ventilation patterns, air quality, and thermal comfort. To enhance urban planning strategies, a suitable climatic classification system is essential for distinguishing different zones based on their environmental conditions. Climatic zoning facilitates the identification of distinct climatic features, enabling region-specific planning and management.
Traditional climate zoning methods are insufficient for modern urban environments due to variations in land use, land cover, urban geometry, and structure. This research employs an applied approach, using descriptive and analytical methodologies. The study integrates multiple spatial data layers, including digital elevation models, land use/cover, building density, green spaces, and hydrographic networks, to classify urban climate zones effectively. These parameters provide a comprehensive understanding of Tehran's climatic conditions and their spatial distribution.
Study Area
Tehran, spanning 615 square kilometers, is situated between mountainous zones and arid plains, leading to diverse climatic conditions. The city's climate is primarily influenced by its topography, with the northern highlands experiencing more favorable conditions than the central and southern low-altitude plains.
Local climatic differences arise due to varying land uses, such as green spaces, barren lands, asphalt surfaces, and residential zones. Building density significantly impacts the urban climate, contributing to distinct microclimatic conditions across different localities. The city's morphology and topography play a decisive role in shaping its climatic response units.
Discussion
A geomorphological map provides valuable insights into the shape, structure, and texture of Tehran’s urban landscape. This map illustrates the relationship between natural features, built environments, and climatic conditions. Different neighborhoods within Tehran exhibit unique topographic characteristics, construction patterns, traffic densities, and accessibility, all of which influence local climate variations.
Key homogeneous climate response units in Tehran include mountains (class 3), green spaces (class 16), and riverbeds/lakes (class 17). These units contribute positively to reducing air temperature, enhancing air quality, and promoting natural ventilation. Preserving these areas is crucial for mitigating urban heat island effects and improving urban climate resilience.
To assess Tehran’s climate at a localized scale, topographic and urban structural parameters were analyzed. First, the spatial distribution of building density was classified into five distinct groups. Subsequently, a geomorphological map of Tehran was generated, identifying ten morphological classes. By integrating building density and urban geomorphology data, a homogeneous climate response unit (HCR) map was developed. This map serves as a vital tool for understanding and managing Tehran’s urban climate.
Conclusion
This research introduces a novel approach to urban climate zoning, previously applied in Lisbon, Portugal, for classifying urban climatic conditions. Central Tehran exhibits high building density, limited green spaces, and pronounced urban heat island effects. The primary factors contributing to the urban heat island phenomenon include high population density, intensified urban activities, and dense construction patterns.
The geomorphological analysis highlights that central and southern Tehran, particularly districts with minimal green spaces (e.g., District 9), suffer from poor air quality and inadequate natural ventilation. These areas exhibit unfavorable climatic conditions due to high pollution levels, urban congestion, and limited airflow. Conversely, northern Tehran (e.g., Districts 1 and 4) benefits from superior air quality, attributed to its proximity to mountains, river valleys, and extensive green spaces.
The prevailing wind direction in Tehran originates from the west, influencing pollutant dispersion patterns. Industrial concentrations in the western parts of the city exacerbate pollution levels in adjacent areas. Consequently, central and southern Tehran require strategic urban interventions to enhance climatic conditions. Recommendations include:
- Integrating green spaces on building facades and streets.
- Establishing water features such as ponds and fountains to moderate air temperature.
- Utilizing reflective and cool materials in urban surfaces to mitigate heat accumulation.
- Expanding green areas to improve air quality and humidity levels.
- Regulating urban expansion to prevent excessive development in climatically vulnerable zones.
- Designing transportation networks to facilitate natural air circulation.
In conclusion, effective climate zoning strategies are essential for sustainable urban development in Tehran. Implementing targeted climate-responsive urban planning measures can significantly improve air quality, thermal comfort, and overall environmental conditions in the city.
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